A fuel cell is a device which uses an electrochemical reaction to convert chemical energy stored in a fuel such as hydrogen or methane into electrical energy. In general, fuel cells include an anode to catalytically react with the fuel and a cathode in fluid communication with an oxidant such as air. The anode and cathode are disposed on opposing sides of an electrolyte material which conducts electrically charged ions therebetween. The electrolyte material and the design of the fuel cell determine the type and performance of the fuel cell. For example, Molten Carbonate Fuel Cells (MCFC) which operate at approximately 650° C. typically include an electrolyte which is a molten liquid during operation.
Fuel cells are typically arranged in a stacked relationship. A fuel cell stack includes many individual cells positioned between a fixed end plate and a free end plate. In some instances the fuel cell stack is contained within an enclosure such as a steel vessel. The enclosure typically includes penetrations extending therethrough. The penetrations are used for the passage of electrical conductors and pipes that provide communication between the fuel cell stack and a balance of plant system located outside of the enclosure. The enclosure defines an interior area that is typically subject to high temperatures and pressures and large temperature and pressure changes. The interior area is therefore sealed off from external areas. Thus, the penetrations have a refractory material therein to seal the penetrations.
The refractory materials have different coefficients of expansion than the materials they seal against, such as a metallic material. In addition, the refractory materials are generally applied at room temperature and are required to tolerate a transition to operation at high temperatures. Typically, the refractory material shrinks during heating, resulting in a loss of sealing at high operating temperatures.